[dmaqtor]

Hello,

I'm not sure what is the difference between acme thread rod and the other threaded rods. but, I couldn't find one. Can I use any threaded rod or it has to be acme precision rod ?

Thanks.

[momus_cnc]

Acme threads are also know as trapezoidal. They have a different thread profile that is designed specifically for efficiently transmitting torque loads.
Trapezoidal thread forms - Wikipedia, the free encyclopedia

If you can't find any suppliers that will ship to your location, I may have an extra piece that I could sell you. I'll have to take a look through my pile of parts. Whatever threaded rod you use for the Z leadscrew, you'll need to be able to get an anti-backlash nut with the same threads.

-Bob

[cs49230]

I bought the 3/8 10 setup from McMasters and DumpsterCNC.

I had some 1/2 8 3 start rod salvaged from an old garage door opener. But couldn't find any nuts to work with it. I had a block of nylon and looked at making my own nut. I built a jig and mounted it all up. Put in oven at 230 degrees for about 45 minutes. This softened the plastic enough I was easily able to thread the rod threw a pilot hole. After cooling the thread was very tight and required a moderate torque to turn the rod.

So after buying the parts find that it takes almost as much torque to turn the rod as my experiment. Seems like too much to me.. I'll coat the rod and nut threads with some wax and see how that works.

[OCNC]

Seems like too much to me.. I'll coat the rod and nut threads with some wax and see how that works.

Grind a groove in one end of the rod in the axial direction to make a simple tap. Then screw the end into the plastic nut to cut a 'perfect' fit.

Chris

[momus_cnc]

The following is quoted from the DumpsterCNC FAQ page
dumpsterCNC

What if my nuts are too tight?
Umm... ok... They shouldn't be too tight, only snug and you should be able to turn them with a finger and thumb, you shouldn't have to grip them for them to turn. All lead screws are not created equally, if you use a different supplier than I recommend (sometimes even the same supplier!), they may fit differently. We've had good luck when I suggest to file 2 or 3 notches around the last 2-3 threads of the lead screw and force it through the back of the leadnut only under the flange area, basically working as a custom tap; it usually doesn't take much. You are welcome to try this, otherwise, you can return them and I'll see if I can open them up here.

[dmaqtor]

Acme threads are also know as trapezoidal. They have a different thread profile that is designed specifically for efficiently transmitting torque loads.
Trapezoidal thread forms - Wikipedia, the free encyclopedia

If you can't find any suppliers that will ship to your location, I may have an extra piece that I could sell you. I'll have to take a look through my pile of parts. Whatever threaded rod you use for the Z leadscrew, you'll need to be able to get an anti-backlash nut with the same threads.

-Bob

I'm still looking for supplier provides international shipping for the acme thread rod. Thanks I will contact you if I couldn't find any.

[moki]

While you guys are on the subject of threaded rod, I am busy putting together a small CNC machine using aluminium 25 x 25 mm tube. I have 8mm UNF (24TPI) as well as 6mm UNF (28TPI) stainless steel threaded rod. Which one should I use? My machine frame will be 400mm x 600mm. It will be used for PCB milling, plastics and maybe light aluminium. I also have 3 Nema 23 motors - 9kg/cm torque.

Thanks in advance

[momus_cnc]

I have 8mm UNF (24TPI) as well as 6mm UNF (28TPI) stainless steel threaded rod. Which one should I use? My machine frame will be 400mm x 600mm.

The difference in resolution when using either of those will be minimal, and both will give a resolution far, far in excess of the rigidity of your machine. The resolution is also far in excess of the accuracy/manufacturing tolerances of the rod itself. You don't say what you are using for stepper drives, but if the steppers are 200 steps per inch, even at full stepping you will have an electronic resolution of .0002" per step with the 24tpi rod. At 10x microstepping you are looking at 48,000 steps per inch, or .00002".

If those are the only two options I'd go with the 8mm. You have deeper thread engagement, it is a stiffer rod, and jogging will be just a little less painfully slow. But I think I'd seriously consider looking for rod with fewer threads per inch. If your frame is 600mm in the long direction, I'm guessing your travel is probably somewhere around 400mm, and jogging over that distance will feel like it takes days.

Also, 25mm aluminum tubing isn't very stiff for a machine that size, so unless you are configuring it in a particularly clever way, I wouldn't count on milling too much aluminum with the machine. It will most likely be too flexible, creating chatter, broken cutters, etc. Plastics and PCBs sounds like a more achievable goal.

-Bob

[moki]

Thanks for the response Bob. I have 8mm UNC (18TPI) & 10mm UNC (16TPI) both in stainless steel as well. The motors have a shaft diameter of 6.35mm (1/4 inch). They are rated at 2A 3.6v and 1.8 deg/step - 200 steps per revolution. Do you think I should make the machine shorter in the long direction and if so by how much? Or should I just abandon aluminium and use MDF or plywood instead. I am new to this and would appreciate any help and advice.

[beggnercnc]

i have recently completed the build on a diy cnc machine i use 5/16 18 tpi threaded rods for ballscrews, i have a cheap off ebay motors and controllers i believe it's the tb6560, not sure what the stepping is set to on the board and mach 3 settings are confusing. the problem is that the machine moves so slow that i can hardly tell it is moving. should i put in 1/2 threaded rod or maybe it's just my settings,i am also not sure how i should adjust or calculate to adjust my machine
any help is appreciated!

[vtxstar]

I am not familiar with Mach3 but it sounds like you do not have the tpi/motor setup correct or the controllers are not being commanded to drive at a rate for fast movement.

Are you running the belt drive on X and Y and using the posted screw drive for Z as normal in the plans?

-=Doug